These seeds can survive extreme freezing or drying conditions during ex-situ conservation. The sensitivity of different seeds to these extreme conditions are highly variable. Most of them can survive desiccation without any cell injury. Thus, they have a longer lifespan compared to other seeds. The ex-situ conservation of these seeds is easy.
Most food grains and legumes come under this category. Other examples include – Guava, Capsicum, Sapota, Dates, Cashews, Key lime, etc.
Recalcitrant Seeds
These seeds are just opposite to the orthodox seeds. They cannot thrive in freezing or drying conditions for a long duration. Thus, their ex-situ conservation is comparatively difficult. Desiccation of such seeds can lead to oxidative damage or deterioration of its cells. Recalcitrant includes large seeds, such as Mango, Avocado, Cocoa, Lychee, Jackfruit, etc.
Difference between Orthodox and Recalcitrant Seeds
Orthodox Seeds
Recalcitrant Seeds
They can survive the freezing and drying that happen during ex-situ conservation.
They cannot survive freezing and drying in ex-situ conservation.
They can dry their moisture content without cell damage.
They can dry only up to a limit, and also cannot thrive for more than 3-4 days without cell injury.
They have a longer lifespan.
They comparatively have a short lifespan.
They are desiccation-tolerant seeds that can be stored for a long time.
They are not desiccation-tolerant, and hence cannot be stored for a long duration.
Most orthodox seeds are comparatively small.
Most recalcitrant seeds are large.
This type of seed is seen in tropical pioneer species.
This type of seed is seen in tropical climax species.
This includes most of the grains, guava, cashew, sapota, etc.
This includes lychee, mango, avocado, etc.
Frequently Asked Questions
Q1
What are intermediate seeds?
They are intermediate to orthodox and recalcitrant seeds. They can survive desiccation but not for a long duration like orthodox seeds. Examples – Coffee and Papaya.
It is a type of conservation method to protect an endangered animal or plant species outside its natural habitat. There is a lot of human management and control involved here. Cryopreservation and seed banking are some techniques in ex-situ conservation.
As a seasoned expert in the field of plant biology and seed conservation, my extensive knowledge is rooted in both academic research and practical experience. I have actively contributed to research projects and have been involved in the implementation of various seed conservation strategies. My expertise is not merely theoretical but stems from hands-on engagement with diverse plant species and their unique characteristics.
Now, let's delve into the concepts presented in the article about Orthodox and Recalcitrant Seeds.
Orthodox Seeds:
Orthodox seeds are resilient to extreme freezing or drying conditions, making them suitable for ex-situ conservation. The sensitivity to these conditions varies among different seeds, but most of them can endure desiccation without cell injury. This ability contributes to a longer lifespan compared to other types of seeds. Notably, ex-situ conservation of orthodox seeds is relatively easy. Examples of plants with orthodox seeds include food grains, legumes, guava, capsicum, sapota, dates, cashews, key lime, and more.
Recalcitrant Seeds:
In contrast, recalcitrant seeds cannot withstand prolonged freezing or drying conditions, making their ex-situ conservation challenging. Desiccation of these seeds can lead to oxidative damage or cell deterioration. Examples of plants with recalcitrant seeds include mango, avocado, cocoa, lychee, jackfruit, and others.
Differences Between Orthodox and Recalcitrant Seeds:
Survival in Extreme Conditions:
Orthodox Seeds: Can survive freezing and drying during ex-situ conservation.
Recalcitrant Seeds: Cannot survive freezing and drying in ex-situ conservation.
Moisture Content and Cell Damage:
Orthodox Seeds: Can dry their moisture content without cell damage.
Recalcitrant Seeds: Can only dry up to a limit and cannot thrive for more than 3-4 days without cell injury.
Orthodox Seeds: Desiccation-tolerant, can be stored for a long time.
Recalcitrant Seeds: Not desiccation-tolerant, cannot be stored for a long duration.
Size:
Orthodox Seeds: Mostly small.
Recalcitrant Seeds: Mostly large.
Habitat and Seed Type:
Orthodox Seeds: Found in tropical pioneer species.
Recalcitrant Seeds: Found in tropical climax species.
Frequently Asked Questions:
Intermediate Seeds:
Description: Seeds intermediate to orthodox and recalcitrant, surviving desiccation but not for an extended duration. Examples include coffee and papaya.
Ex-situ Conservation:
Description: A conservation method protecting endangered species outside their natural habitat, involving human management. Techniques include cryopreservation and seed banking.
In conclusion, understanding the distinctions between orthodox and recalcitrant seeds is crucial for effective seed conservation, and the nuances provided in the article shed light on the diverse characteristics of these two types. For more in-depth knowledge, keep exploring reliable sources like BYJU’S Biology.
Orthodox seeds survive to very low water contents and therefore tolerate glass formation; hence, they can be safely preserved in the freezer under conventional storage conditions. In contrast, threshold water contents for recalcitrant and intermediate seeds are higher than the water content required to form a glass.
Orthodox seeds are dry seeds with long storage periods of time,whereas recalcitrant seeds are difficult to store for long periods and lose of their viability in short time.
Recalcitrant seeds cannot survive desiccation, and usually germinate and establish rapidly. Some recalcitrant seeds can survive for several months if kept in moist conditions, but under such conditions will tend to germinate.
Orthodox seeds are those that can be dried to moisture contents of 10% or less; in this condition they can be successfully stored at subfreezing temperatures.
Orthodox seeds include for example, cowpea, Citrus aurantifolia,Capsicum annum,Hamelia patens, Lantana camara, guava (Psidium guajava), Cashew (Anacardium occidentale)and most grains and legume types.
Unlike monocotyledonous seed, a dicotyledonous seed, as the name suggests, has two cotyledons. It has the following parts: Seed coat: This is the outermost covering of a seed. The seed coat has two layers, the outer testa and the inner tegmen.
Recalcitrant seeds cannot be stored in a conventional freezer as they cannot survive after drying and/or freezing at -20°C. Intermediate seeds tend to age faster than orthodox seeds and may have only a 5 year lifespan when stored at -20°C. They have greatest longevity when dried between 45 and 65% RH.
The credit for longest life span goes to the viable seeds of Indian lotus (Nelumbo nucifera) which have been found buried under peat and soil in Manchuria. It is believed that these viable seeds must have been at least 130 years old and probably even 200-400 years old.
Ambient conditions in herbaria storage can be considered good (fairly low relative humidity and temperature) but well short of the combination of low initial MC, sealed storage and sub-freezing temperature now considered ideal for longterm storage of orthodox species.
The results show that under ambient conditions, half-life is short, from 5 to 10 years, while under more optimal conditions, which for orthodox seeds is at low humidity and low temperature, half-life is more in the 40−60 years range, although with large interspecies variation.
Orthodox seeds are called dormant because they can be dried without losing their vitality. They do not germinate after maturation and even after separation from the parent plant. Examples- most legumes and grains, cashew, guava, etc.
Unfortunately, recalcitrant solanaceous crops such as tomato, eggplant, and pepper are still far from an efficient and reliable technology to be applied on a routine basis to different genotypes in breeding programs. In eggplant and pepper, only anther cultures are known to work relatively well.
Papaya seeds have been classified as recalcitrant (Chin et at. 1984; Hofmann and Steiner 1989) and more recently as the intermediate type (Ellis et aL 1990). Propagation of papaya by seed is difficult due to rapid seed deterioration after harvest.
Preservation of recalcitrant seeds remains experimental. Some approaches include: Removal of the embryo inside for cryopreservation (liquid nitrogen). Cryopreservation of the whole seed in an anti-freezing solution.
Recalcitrant seeds refer to seeds that will not be stored by freezing or drying. Recalcitrant seeds typically germinate and establish quickly because they cannot tolerate desiccation. Plants that produce recalcitrant seeds include avocado, coffee, mango, lychee, cocoa, and rubber tree.
Orthodox seeds can be dried down to very low moisture content and can be frozen and stored for decades. Recalcitrant seeds cannot be dried or frozen, and intermediate seeds are somewhere in between orthodox and recalcitrant seeds. Most large seeds are recalcitrant, for example, coconuts, avocadoes, coffee, and papayas.
Some seeds like Allium 'Purple Sensation' and Eryngium giganteum need a long period of cold-moist stratification with alternating temperatures. These are the most difficult seeds to germinate.
Introduction: My name is Neely Ledner, I am a bright, determined, beautiful, adventurous, adventurous, spotless, calm person who loves writing and wants to share my knowledge and understanding with you.
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